This invention relates to an apparatus for recording and detecting a cue signal used in cueing the contents of a recorded data.
With a dictation apparatus or handy type tape recorder, for example, a cue signal is recorded as a rule on a recording tape in order to quickly detect the position of a particular recorded data. The following are the typical methods of recording a cue signal.
(1) A cue signal having such a low frequency (sine wave of less than 100 Hz) as lets the listener feel little concern at the time of playback is overlapped on a voice signal. United States patent application Ser. No. 138,195, filed Apr. 7, 1980, entitled "Cue Signal Recording Apparatus" (Inventor: Kenji Fujibayashi) and assigned to Olympus Optical Co., the same assignee as the present patent application may be cited as an embodiment of this process (1), though not constituting prior art with respect to the present patent application.
(2) A voice signal to be recorded is temporarily shut off. A cue signal of a specified form is recorded in that part of a tape in which a voice signal is not recorded.
(3) An exclusive cue signal track is formed in a tape. A cue signal of a specified form is recorded in this track. This arrangement is set forth in, for example, U.S. Pat. No. 4,007,491.
The method (3) ensures the relatively easy detection and subsequent processing of a cue signal and gives rise to few errors in detection. However, the requirement of an exclusive track decreases the width of tracks necessary for the recording of proper data, thereby reducing the efficiency of utilizing a tape. When, therefore, applied to a midget tape recorder such as a microcassette type, the method (3) is likely to raise problems such as deterioration of the S/N ratio and change in the signal level. In contrast, the methods (1) and (2) utilize voice-recording tracks for the impression of a cue signal without any loss in a tape-using efficiency. Since, however, the same track is applied to the recording of voice signals and cue signals, complication tends to arise in the detection of a cue signal and the subsequent processing thereof, and more errors are likely to occur in detection than in the method (3).
In the case of a midget tape recorder such as a microcassette type where the effective utilization of a tape bears a particularly great importance, the method (3) is unadapted for application. Therefore, the method (1) or (2) is still often accepted, though a somewhat complicated signal-processing circuit is involved. Problems resulting from the complication of a signal-processing circuit have come to be resolved by the development of integrated circuit techniques. Nevertheless, the method (1) or (2) is accompanied with the drawback that errors are apt to occur in the detection of a cue signal. Such errors mainly arise from the fact that the running speed of a tape is not accurately controlled when a cue signal is to be detected. At the time of normal recording-playback, a tape is made to travel by driving a capstan, thereby ensuring an accurate tape feed speed. Conversely where a cue signal is detected, the tape is made to run by driving a reel. Therefore, the running speed of the tape becomes unstable and noticeably varies with the progressively-increasing diameter of a roll of a taken up tape, presenting difficulties in accurately detecting a cue signal.